Rollcage on the street

[LLave]

I recently came to the realization that realistically my car will be much more of a street car then a race car. So, rather then building a ineffective race car that is a poor street car I have decided to shift my focus a bit more toward the true use of the car. I want an aggressive street car that I can have fun with on the track on occasion.

 

The question is what are the merits and dangers of a cage in a street car? I am no engineer but my "gut feeling" tells me the S30 chassis is not exactly the safest thing on the road; especially with a decently potent SBC powering it. The added impact protection of a rollcage is certainly desirable. The danger of smashing my helmetless head into a piece of tubing however is not. Do you think that a properly designed cage that is pushed absolutely as far away from the drivers head as possible and padded, combined with a quality seat (OMP's in my case) and harnesses can prevent the drivers head from impacting the tubing and provide a street safe cage? I can probably design it so that my head is clear of all the cage members but what about during an impact when the chassis my distort?

 

I guess I am a bit nervous about re-engineering the safety system of the chassis and I am wondering how bad the stock S30 really is and if I will do more harm them good.

 

I apologize if this question got a bit lengthy.

[Dayz]

Well, in my book, if I get T-Boned in my 1970, I will look like nothing usefull! Have a look in those doors. The S30 is a thin can, with the engine coming right beside the 2 occupant in a front collision crash.

 

With all that said, I personally would run a cage, maybe not a full one but at least with the sidebars (6 point). I have the same goal as you in mind and I will run a full cage.

 

At the end of the day, they say that in an accident, what you can touch with your hand, you can/will hit it with your head at the time of impact.

 

I am subscribing to this thread for sure,

Dayz

[johnc]

I build roll cages for a living. I will not put a full cage in a car that's driven by an un-helmeted driver. A 1.75" OD x .095" wall tube will not give when your head hits it and concentrates the impact force into a 1 to 2 square inch area. Have a friend hit you over the head with a piece of roll bar tubing swung as fast and as hard as he can. He may be able to swing that tube at 50 mph if he's a major league ball player.

[johnc]

With all that said, I personally would run a cage, maybe not a full one but at least with the sidebars (6 point). I have the same goal as you in mind and I will run a full cage.

 

Unfortunately, without the front structure that comes with a proper roll cage, the front mounting points for your door bars make the bars dangerous in a side impact. What's going to keep the front of the door bars from bending inward, breaking the seat, and crushing your legs during the impact as the floor pan crumples?

 

Remember, drag racing style roll bars/cage are not designed to handle hard side impact. They are designed for single car accidents.

[JMortensen]

Do you think that a properly designed cage that is pushed absolutely as far away from the drivers head as possible and padded, combined with a quality seat (OMP's in my case) and harnesses can prevent the drivers head from impacting the tubing and provide a street safe cage? I can probably design it so that my head is clear of all the cage members but what about during an impact when the chassis my distort?

I don't think it is possible in an S30 to get the tube far enough away from the driver's head to make impact an impossibility. I think with some of the newer cars that have a higher waistline and a taller greenhouse you could do it if the seat was mounted lower than stock. On an S30 there just isn't that much space inside the car to work with.

[LLave]

Thank you for the feedback. I appreciate it.

 

So it sounds like the consensus so far is that working with in the confines of the S30 it is not be possible to place the tubing far enough away from the drivers head to make the chance of impact impossible (err... highly unlikely*). Even with a very low seat and harness.

 

Although in the event of a side impact the drivers head is most likely going to impact some portion of the interior. I am not sure that I am convinced a *properly* padded tube is much worse then the interior of a S30. Could something like this below be much worse then a flat piece of metal?

 

 

If a full cage is not possible to safely execute what sort of chassis reinforcement would you recomend to improve rigidity and safety?

[JMortensen]

Although in the event of a side impact the drivers head is most likely going to impact some portion of the interior. I am not sure that I am convinced a *properly* padded tube is much worse then the interior of a S30. Could something like this below be much worse then a flat piece of metal?

Regardless of whether or not it would be worse for your head, you'd be much more likely to hit it.

 

If a full cage is not possible to safely execute what sort of chassis reinforcement would you recomend to improve rigidity and safety?

How about just a good roll bar, perhaps with some subframe connectors and rocker modifications?

[LLave]

Regardless of whether or not it would be worse for your head, you'd be much more likely to hit it.

 

Good point. Even if you assume the 2 surfaces to be equal the bar, at the least moves the surface 2 inches close to your face.

 

 

How about just a good roll bar, perhaps with some subframe connectors and rocker modifications?

 

Some baddogs, a good roll bar (my current hoop with some bracing) and a length of tubing stitched into the rocker sounds like a good plan for increasing the chassis rigidity for the street but it doesn't really help too much with side impact on the door.

[JIM73240Z]

alot of people here have said that if you want a safer car on the street then go get a safer car. a full cage will help but at the expence of your head. i do not think there is any way to help the doors out at all in a side impact. the doors are too low, too thin, too old. a normal sedan has the bumper right at mid height, let alone an suv where the bumper comes over the window sill. i know where you are going and i have thought about it myself as wanting a full track car and streetable, but they are mutualy exclusive. best of luck.

 

+1 with what jon said. rool bar, with harness bar. seats and subframe connectors.

 

jimbo

[Tony D]

There has been some work in Europe on a Roll Cage utilizing Chrome-Moly Tubing that is put inside the original crash structures of the car...

 

But we are talking that involves some very detailed body disassembly, and competent calculations. The shop doing it does FIA Certified Roll Cage Engineering, and the proprietor is a former F1 Team Engineer from the 80's.

 

It's neat from what I saw of it...reminiscent of Tim Allen's "Hidden Cage" Saleen done up a few years back.

 

That kind of tells you the costs involved in properly designing and installing a 'street safe' roll structure. At least one that is mostly hidden from view.

[tube80z]

You could take a few clues from newer cars. Almost all have a stout bar running across the dash expanse tied into the door frames. And they have a bar across the car below the seats. I'd also think in a S30 a rear strut bar could serve some function in side impact, assuming it's a little bigger than normal. And the bars from the front of the rockers to the TC boxes would help some to spread load from a side hit. If you have a really old S30 consider some newer doors with door beams.

 

Cary

[LLave]

There has been some work in Europe on a Roll Cage utilizing Chrome-Moly Tubing that is put inside the original crash structures of the car...

 

But we are talking that involves some very detailed body disassembly, and competent calculations. The shop doing it does FIA Certified Roll Cage Engineering, and the proprietor is a former F1 Team Engineer from the 80's.

 

It's neat from what I saw of it...reminiscent of Tim Allen's "Hidden Cage" Saleen done up a few years back.

 

That kind of tells you the costs involved in properly designing and installing a 'street safe' roll structure. At least one that is mostly hidden from view.

 

I did consider cutting into the roof support structure above the down bars and sort of recessing them in. Nothing as pretty for high tech as you are describing. That is an option to get the bars as far away from the driver as possible. But the more I think about it the less hell bent I am on installing a roll cage.

[LLave]

You could take a few clues from newer cars. Almost all have a stout bar running across the dash expanse tied into the door frames. And they have a bar across the car below the seats. I'd also think in a S30 a rear strut bar could serve some function in side impact, assuming it's a little bigger than normal. And the bars from the front of the rockers to the TC boxes would help some to spread load from a side hit. If you have a really old S30 consider some newer doors with door beams.

 

Cary

 

Excellent suggestions. I will look for an opportunity to safely brace the door jam areas.

 

At this point I am going to mock up my current cage and seat combination and spend some time with a tape measure. I will most likely end up putting that cage on the shelf until I get around to building a real track car.

[LLave]

Here is a link to an interesting discussion on the topic of cage padding.

http://forums.nasioc.com/forums/showthread.php?t=719280

[JustinOlson]

This stuff looks cool:

 

http://www.safedrives.com/proddetail.asp?prod=BSCI-DDpad&cat=105

 

Justin

[sickboy]

Here is a pic of my cage, it is a compromise because the car is still street legal and is driven around town occasionally (I did not want to have to climb in and out of the car). I agree, a hard side impact would most likely end me without a helmet on.

[Silver Mine Motors]

I thought I would offer some personal advise about my experience with the safety of my past z cars. I have been in two major accidents with my 260zs. Both cars were totaled and both cars had strep bars but no roll bars. The first time I was going about 45 mph and had a head on collision with another car going about the same speed as I was. The car was totaled but I was fine. I barley had a scratch on me. The car was completely totaled, and had to be flatbeded to the junk yard. I think what saved me that time was the fact that the body took the impact. The second time was the same scenario but with a tree, and it was during a left turn.

 

So as far as front impact our cars are pretty good. I think side impact is the only area were I would like to have a little more safety. Especially since our doors are so light. I'd like to see what type of roll cage you decide to make that would not get in the way, but would reduce the probability of getting hurt during side impact.

[EMWHYR0HEN]

Here is a pic of my cage, it is a compromise because the car is still street legal and is driven around town occasionally (I did not want to have to climb in and out of the car). I agree, a hard side impact would most likely end me without a helmet on.

 

Thats and interesting setup. Care to share more pics?

[essdeezee]

Ever heard of a japanese fabrication/tuning shop called Opera Performance? Me neither, until I ran across this article a few years back in Sport Compact Car.

 

The issue featured articles on three different cars built by the shop, each for a different purpose, and each with different methods for getting to the end result.

 

How is this relevant to this discussion?

 

Check the link to the article, page three especially.

 

http://www.sportcompactcarweb.com/features/0611sccp_opera_performance_honda_rsx/index.html

 

The goal was to have the stiffness of a caged car, but not sacrifice the safety of the occupants.

 

Ever since I first saw this article, I thought the engineering methods employed were wonderful and could be applied to the Zcar.

 

What say you? It seems like a great compromise for a dual purpose vehicle.

[Mikelly]

I had a full cage in a street/track Zcar back in 1995 and it was in a total loss accident... I had my "racing" harnesses on (5 point JRZs) and the accident consisted of a heavy duty "plumbing truck" with lots of hardware/tools loaded up in it (large box truck) rearending me and pushing the car into the back of a Ford Taurus sedan. My head hit the halo on the roll bar. Even though the halo bar was padded, I had a concussion.

 

I'll never own another street driven car with a "full cage"...

 

Mike

 

Thank you for the feedback. I appreciate it.

 

So it sounds like the consensus so far is that working with in the confines of the S30 it is not be possible to place the tubing far enough away from the drivers head to make the chance of impact impossible (err... highly unlikely*). Even with a very low seat and harness.

 

Although in the event of a side impact the drivers head is most likely going to impact some portion of the interior. I am not sure that I am convinced a *properly* padded tube is much worse then the interior of a S30. Could something like this below be much worse then a flat piece of metal?

 

 

If a full cage is not possible to safely execute what sort of chassis reinforcement would you recomend to improve rigidity and safety?